;---------------------------------------------------------------------
;
; File: example_a.sexp
; Using list operations in SIF01.
;
; Copyright (C) 2006-2008 by Ariel Ortiz <ariel.ortiz@itesm.mx>
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program.  If not, see <http://www.gnu.org/licenses/>.
;
;---------------------------------------------------------------------

(define lst (quote (a b c)))

(define duplicate
  (fn (lst)
    (if (null? lst)
        ()
        (cons (first lst)
              (cons (first lst)
                    (duplicate (rest lst)))))))

                   ; Displayed results:
                   ;
lst                ;         (a b c)
(first lst)        ;         a
(rest lst)         ;         (b c)
(first (rest lst)) ;         b
(duplicate lst)    ;         (a a b b c c)